The goal of this research is to relate the chemical properties of tentoxin, including conformation and structural variations to its mechanism of action. Tentoxin is the cyclic tetrapeptide, cyclo (N- Methyl-L-alanyl-L-leucyl-N-methyl-Z-dehydrophenylalanyl-glycyl). The research will proceed toward chemical synthesis of analogs, determination of their conformations and activities, and determination of the mechanism of action. Additional goals are determining the effects of N-methyl dehydroamino acid residues on the conformation of linear peptides and developing new methods for synthesizing cyclic peptides difficult to prepare by conventional methods.